It is the purpose of this investigation to document the effects of changing pH and Al, Cu, Pb and Zn toxicity on freshwater lake algae. We will focus the study on cellular changes and the growth rates of the algae at different pH in the presence and absence of Al, Cu, Pb and Zn. Specifically, the objectives of this study are: 1. Determine the effect of changing pH from 9.0 to 3.0 on the growth of selected representative freshwater lake algae. 2. Determine the EC50 of Al, cu, Pb and Zn at the different pHs used in this study. 3. Determine cellular effects using morphometry at the different pHs tested and the effect of Al, Cu, Pb and Zn at the EC50 and one log concentration above and below this point. 4. Determine the effect of each treatment on the chlorophyll content of the cells. This is a good estimate of productivity. 5. Determine using X-ray energy dispersive analysis with a scanning transmission electron microscope if compartmentalization of the Al, Cu, Pb, and Zn has occurred. 6. To establish the toxicity hierarchy among these four cations at the varying pH levels in order to determine the importance of Al as a key toxicant in acidogenesis. It is felt, in order to understand the toxic effects of heavy metals to cell systems, that it is necessary to document how pH alterations effect the mobilization of these metals at the cellular and intracellular level. This project is designed to address this question.